When does the growth rate of a population following the logistic model equal zero? The logistic model is given
As dN/dt=rN(1─N/K)
1. when N/K is exactly one.
2. when N nears the carrying capacity of the habitat.
3. when N/K equals zero.
4. when death rate is greater than birth rate.

Which of the following is correct for r-selected species?
1. Large number of progeny with large size.
2. Small number of progeny with small size.
3. Small number of progeny with large size.
4. Large number of progeny with small size.

If ‘+’ sign is assigned to beneficial interaction, ‘─’ sign to detrimental and ‘0’ sign to neutral interaction, then the
Population interaction represented by ‘+’ ‘─’ refers to
1. amensalism.
2. commensalism.
3. parasitism.
4. mutualism.

Mycorrhiza are the example of
1. Amensalism.
2. Antibiosis.
3. Mutualism.
4. Fungistasis.

Natality refers to
1. Number of individuals leaving the habitat
2. Birth rate
3. Death rate
4. Number of individuals entering a habitat

Which one of the following population interactions is widely used in medical science for the production of
antibiotics?
1. Parasitism
2. Mutualism
3. Commensalism
4. Amensalism

A keystone species is the one which has
1. A small proportion of total biomass but has huge impact on community’s organisation and survival
2.A plenty of biomass but low impacts on community’s organisation
3. A rare species with little impact on biomass and other species in the community
4. A dominant species which has a large proportion of biomass and which affects many other species

A system of rotating crops with legume or grass pastures to improve soil structure and fertility is called:

1. Shifting agriculture
2. Ley farming
3. Contour farming
4. Strip farming

It is much easier for a small animal to run uphill than for a large animal, because:
1. The efficiency of muscles in large animals is less than in the small animals.
2. It is easier to carry a small body weight.
3. Smaller animals have a higher metabolic rate.
4. Small animals have a lower ${\mathrm{O}}_2$ requirement.

Which one of the following characteristics is not shared by birds and mammals? 
1. Warm blooded nature 

2. Ossified endoskeleton

3. Breathing using lungs

4. Viviparity